(1) Field of the Invention
The present invention relates to a process for synthesizing aminoarylboronic esters of the general formula wherein R, R2, and R3 are each independently an alkyl, aryl, vinyl, alkoxy, carboxylic esters, amides, or halogen; Ar is any variety of phenyl, naphthyl, anthracyl, heteroaryl; and R1 is alkyl, hydrogen, or aryl. The aminoarylboronic esters are produced via the metal-catalyzed coupling of arylboronic esters of the general formula wherein R and R1 are any non-interfering group and X is chloro, bromo, iodo, triflates, or nonaflates to amines (primary and secondary). In particular, the present invention provides a process for the synthesis of the aminoarylboronic esters via a step-wise or tandem process in which one catalytic event is a metal-catalyzed borylation and the other catalytic event is a metal-catalyzed amination.
(2) Description of Related Art
There is no single method established for the synthesis of aminoarylboronic esters in the prior art. The most common method involves the derivatization of 3-amino-phenylboronic acid (See for a recent example; Gravel et al., J. Org. Chem. 67: 3 (2002)), which in turn was originally synthesized from 3-bromonitrobenzene via (i) grignard formation, (ii) reaction with a alkylborate followed by hydrolysis, (iii) and reduction of the nitro group (See, Bean and Johnson, J. Am. Chem. Soc. 54: 4415 (1932)).
Therefore, there remains a need for a process for synthesizing aminoarylboronic esters and substituted anilines from arenes that is safer and less laborious than the prior art methods.